draft-ietf-dprive-problem-statement-00.txt		draft-ietf-dprive-problem-statement-01.txt
	Network Working Group S. Bortzmeyer		DNS PRIVate Exchange (dprive) Working Group S. Bortzmeyer
	Internet-Draft AFNIC		Internet-Draft AFNIC
	Intended status: Informational October 26, 2014		Intended status: Informational January 7, 2015
	Expires: April 29, 2015		Expires: July 11, 2015
	DNS privacy considerations		DNS privacy considerations
	draft-ietf-dprive-problem-statement-00		draft-ietf-dprive-problem-statement-01
	Abstract		Abstract
	This document describes the privacy issues associated with the use of		This document describes the privacy issues associated with the use of
	the DNS by Internet users. It is intended to be mostly an analysis		the DNS by Internet users. It is intended to be mostly an analysis
	of the present situation, in the spirit of section 8 of [RFC6973] and		of the present situation, in the spirit of section 8 of [RFC6973] and
	it does not prescribe solutions.		it does not prescribe solutions.
	Discussions of the document should take place on the DPRIVE working		Discussions of the document should take place on the DPRIVE working
	group mailing list [dprive].		group mailing list [dprive].
	skipping to change at page 1, line 36		skipping to change at page 1, line 36
	Internet-Drafts are working documents of the Internet Engineering		Internet-Drafts are working documents of the Internet Engineering
	Task Force (IETF). Note that other groups may also distribute		Task Force (IETF). Note that other groups may also distribute
	working documents as Internet-Drafts. The list of current Internet-		working documents as Internet-Drafts. The list of current Internet-
	Drafts is at http://datatracker.ietf.org/drafts/current/.		Drafts is at http://datatracker.ietf.org/drafts/current/.
	Internet-Drafts are draft documents valid for a maximum of six months		Internet-Drafts are draft documents valid for a maximum of six months
	and may be updated, replaced, or obsoleted by other documents at any		and may be updated, replaced, or obsoleted by other documents at any
	time. It is inappropriate to use Internet-Drafts as reference		time. It is inappropriate to use Internet-Drafts as reference
	material or to cite them other than as "work in progress."		material or to cite them other than as "work in progress."
	This Internet-Draft will expire on April 29, 2015.		This Internet-Draft will expire on July 11, 2015.
	Copyright Notice		Copyright Notice
	Copyright (c) 2014 IETF Trust and the persons identified as the		Copyright (c) 2015 IETF Trust and the persons identified as the
	document authors. All rights reserved.		document authors. All rights reserved.
	This document is subject to BCP 78 and the IETF Trust's Legal		This document is subject to BCP 78 and the IETF Trust's Legal
	Provisions Relating to IETF Documents		Provisions Relating to IETF Documents
	(http://trustee.ietf.org/license-info) in effect on the date of		(http://trustee.ietf.org/license-info) in effect on the date of
	publication of this document. Please review these documents		publication of this document. Please review these documents
	carefully, as they describe your rights and restrictions with respect		carefully, as they describe your rights and restrictions with respect
	to this document. Code Components extracted from this document must		to this document. Code Components extracted from this document must
	include Simplified BSD License text as described in Section 4.e of		include Simplified BSD License text as described in Section 4.e of
	the Trust Legal Provisions and are provided without warranty as		the Trust Legal Provisions and are provided without warranty as
	described in the Simplified BSD License.		described in the Simplified BSD License.
	Table of Contents		Table of Contents
	1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2		1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
	2. Risks . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4		2. Risks . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
	2.1. The alleged public nature of DNS data . . . . . . . . . . 4		2.1. The alleged public nature of DNS data . . . . . . . . . . 4
	2.2. Data in the DNS request . . . . . . . . . . . . . . . . . 4		2.2. Data in the DNS request . . . . . . . . . . . . . . . . . 5
	2.3. Cache snooping . . . . . . . . . . . . . . . . . . . . . 6		2.3. Cache snooping . . . . . . . . . . . . . . . . . . . . . 6
	2.4. On the wire . . . . . . . . . . . . . . . . . . . . . . . 6		2.4. On the wire . . . . . . . . . . . . . . . . . . . . . . . 6
	2.5. In the servers . . . . . . . . . . . . . . . . . . . . . 7		2.5. In the servers . . . . . . . . . . . . . . . . . . . . . 7
	2.5.1. In the resolvers . . . . . . . . . . . . . . . . . . 7		2.5.1. In the recursive resolvers . . . . . . . . . . . . . 8
	2.5.2. In the authoritative name servers . . . . . . . . . . 8		2.5.2. In the authoritative name servers . . . . . . . . . . 8
	2.5.3. Rogue servers . . . . . . . . . . . . . . . . . . . . 9		2.5.3. Rogue servers . . . . . . . . . . . . . . . . . . . . 9
	3. Actual "attacks" . . . . . . . . . . . . . . . . . . . . . . 9		3. Actual "attacks" . . . . . . . . . . . . . . . . . . . . . . 10
	4. Legalities . . . . . . . . . . . . . . . . . . . . . . . . . 9		4. Legalities . . . . . . . . . . . . . . . . . . . . . . . . . 10
	5. Security considerations . . . . . . . . . . . . . . . . . . . 9		5. Security considerations . . . . . . . . . . . . . . . . . . . 10
	6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 10		6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 10
	7. References . . . . . . . . . . . . . . . . . . . . . . . . . 10		7. References . . . . . . . . . . . . . . . . . . . . . . . . . 11
	7.1. Normative References . . . . . . . . . . . . . . . . . . 10		7.1. Normative References . . . . . . . . . . . . . . . . . . 11
	7.2. Informative References . . . . . . . . . . . . . . . . . 10		7.2. Informative References . . . . . . . . . . . . . . . . . 11
	Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 13		7.3. URIs . . . . . . . . . . . . . . . . . . . . . . . . . . 14
			Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 14
	1. Introduction		1. Introduction
	The Domain Name System is specified in [RFC1034] and [RFC1035]. It		The Domain Name System is specified in [RFC1034] and [RFC1035]. It
	is one of the most important infrastructure components of the		is one of the most important infrastructure components of the
	Internet and one of the most often ignored or misunderstood. Almost		Internet and one of the most often ignored or misunderstood. Almost
	every activity on the Internet starts with a DNS query (and often		every activity on the Internet starts with a DNS query (and often
	several). Its use has many privacy implications and we try to give		several). Its use has many privacy implications and we try to give
	here a comprehensive and accurate list.		here a comprehensive and accurate list.
	Let us begin with a simplified reminder of how the DNS works. A		Let us begin with a simplified reminder of how the DNS works.
	client, the stub resolver, issues a DNS query to a server, the		(REMOVE BEFORE PUBLICATION: We hope that the document
	resolver (also called caching resolver or full resolver or recursive		[I-D.hoffman-dns-terminology] will be published as a RFC so most of
	name server). Let's use the query "What are the AAAA records for		this section could be replaced by a reference to it.) A client, the
	www.example.com?" as an example. AAAA is the qtype (Query type), and		stub resolver, issues a DNS query to a server, the recursive resolver
	www.example.com is the qname (Query Name). The resolver will first		(also called caching resolver or full resolver or simply resolver
	query the root nameservers. In most cases, the root nameservers will		recursive name server). Let's use the query "What are the AAAA
	send a referral. In this example, the referral will be to .com		records for www.example.com?" as an example. AAAA is the qtype
	nameservers. The .com nameserver, in turn, will refer to the		(Query type), and www.example.com is the qname (Query Name). The
	example.com nameservers. The example.com nameserver will then return		recursive resolver will first query the root nameservers. In most
	the answer. The root name servers, the name servers of .com and		cases, the root nameservers will send a referral. In this example,
	those of example.com are called authoritative name servers. It is		the referral will be to .com nameservers. The resolver repeats the
	important, when analyzing the privacy issues, to remember that the		query to one of the .com nameservers. The .com nameserver, in turn,
	question asked to all these name servers is always the original		will refer to the example.com nameservers. The example.com
	question, not a derived question. Unlike what many "DNS for dummies"		nameserver will then return the answer. The root name servers, the
	articles say, the question sent to the root name servers is "What are		name servers of .com and those of example.com are called
	the AAAA records for www.example.com?", not "What are the name		authoritative name servers. It is important, when analyzing the
	servers of .com?". By repeating the full question, instead of just		privacy issues, to remember that the question asked to all these name
	the relevant part of the question to the next in line, the DNS		servers is always the original question, not a derived question.
	provides more information than necessary to the nameserver.		Unlike what many "DNS for dummies" articles say, the question sent to
			the root name servers is "What are the AAAA records for
			www.example.com?", not "What are the name servers of .com?". By
			repeating the full question, instead of just the relevant part of the
			question to the next in line, the DNS provides more information than
			necessary to the nameserver.
	Because the DNS uses caching heavily, not all questions are sent to		Because the DNS uses caching heavily, not all questions are sent to
	the authoritative name servers. If the stub resolver, a few seconds		the authoritative name servers. If the stub resolver, a few seconds
	later, asks to the resolver "What are the SRV records of _xmpp-		later, asks to the recursive resolver "What are the SRV records of
	server._tcp.example.com?", the resolver will remember that it knows		_xmpp-server._tcp.example.com?", the recursive resolver will remember
	the name servers of example.com and will just query them, bypassing		that it knows the name servers of example.com and will just query
	the root and .com. Because there is typically no caching in the stub		them, bypassing the root and .com. Because there is typically no
	resolver, the resolver, unlike the authoritative servers, sees		caching in the stub resolver, the recursive resolver, unlike the
	everything.		authoritative servers, sees everything.
	Today, almost all DNS queries are sent over UDP. This has practical		It should be noted that DNS recursive resolvers sometimes forward
	consequences, when considering the encryption of this traffic: some		requests to bigger machines, with a larger and more shared cache, the
	encryption solutions are only designed for TCP, not UDP.		forwarders (and the query hierarchy can be even deeper, with more
			than two levels of recursive resolvers). From the point of view of
			privacy, forwarders are like resolvers, except that the caching in
			the recursive resolvers before them decreases the amount of data they
			can see.
	It should be noted that DNS resolvers sometimes forward requests to		All this DNS traffic is today sent in clear (unencryted), except a
	bigger machines, with a larger and more shared cache, the forwarders.		few cases when the IP traffic is protected, for instance in an IPsec
	From the point of view of privacy, forwarders are like resolvers,		VPN.
	except that the caching in the resolver before them decreases the
	amount of data they can see.		Today, almost all DNS queries are sent over UDP. This has practical
			consequences, when considering a possible privacy technique,
			encryption of the traffic: some encryption solutions are only
			designed for TCP, not UDP.
	Another important point to keep in mind when analyzing the privacy		Another important point to keep in mind when analyzing the privacy
	issues of DNS is the mix of many sort of DNS requests received by a		issues of DNS is the mix of many sort of DNS requests received by a
	server. Let's assume the eavesdropper want to know which Web page is		server. Let's assume the eavesdropper wants to know which Web page
	visited by a user. For a typical Web page displayed by the user,		is viewed by an user. For a typical Web page displayed by the user,
	there are three sorts of DNS requests:		there are three sorts of DNS requests being issued:
	Primary request: this is the domain name that the user typed or		Primary request: this is the domain name in the URL that the user
	selected from a bookmark or choosed by clicking on an hyperklink.		typed or selected from a bookmark or choose by clicking on an
	Presumably, this is what is of interest for the eavesdropper.		hyperlink. Presumably, this is what is of interest for the
			eavesdropper.
	Secondary requests: these are the requests performed by the user		Secondary requests: these are the additional requests performed by
	agent (here, the Web browser) without any direct involvement or		the user agent (here, the Web browser) without any direct
	knowledge of the user. For the Web, they are triggered by		involvement or knowledge of the user. For the Web, they are
	included content, CSS sheets, JavaScript code, embedded images,		triggered by embedded content, CSS sheets, JavaScript code,
	etc. In some cases, there can be dozens of domain names in a		embedded images, etc. In some cases, there can be dozens of
	single page.		domain names in different contexts on a single Web page.
	Tertiary requests: these are the requests performed by the DNS		Tertiary requests: these are the additional requests performed by
	system itself. For instance, if the answer to a query is a		the DNS system itself. For instance, if the answer to a query is
	referral to a set of name servers, and the glue is not returned,		a referral to a set of name servers, and the glue is not returned,
	the resolver will have to do tertiary requests to turn name		the resolver will have to do tertiary requests to turn name
	servers' named into IP addresses.		servers' names into IP addresses. Similarly, even if glue records
			are returned, a careful recursive server will do tertiary requests
			to verify the IP addresses of those records.
			It can be noted also that, in the case of a typical Web browser, more
			DNS requests are sent, for instance to prefetch resources that the
			user may query later, or when autocompleting the URL in the address
			bar (which obviously is a big privacy concern).
	For privacy-related terms, we will use here the terminology of		For privacy-related terms, we will use here the terminology of
	[RFC6973].		[RFC6973].
	2. Risks		2. Risks
	This draft focuses mostly on the study of privacy risks for the end-		This document focuses mostly on the study of privacy risks for the
	user (the one performing DNS requests). Privacy risks for the holder		end-user (the one performing DNS requests). We consider the risks of
	of a zone (the risk that someone gets the data) are discussed in		pervasive surveillance ([RFC7258]) and also risks coming from a more
	[RFC5936]. Non-privacy risks (such as cache poisoning) are out of		focused surveillance. Privacy risks for the holder of a zone (the
	scope.		risk that someone gets the data) are discussed in [RFC5936]. Non-
			privacy risks (such as cache poisoning) are out of scope.
	2.1. The alleged public nature of DNS data		2.1. The alleged public nature of DNS data
	It has long been claimed that "the data in the DNS is public". While		It has long been claimed that "the data in the DNS is public". While
	this sentence makes sense for an Internet wide lookup system, there		this sentence makes sense for an Internet-wide lookup system, there
	are multiple facets to data and meta data that deserve a more		are multiple facets to the data and metadata involved that deserve a
	detailed look. First, access control lists and private name spaces		more detailed look. First, access control lists and private
	nonwithstanding, the DNS operates under the assumption that public		namespaces nonwithstanding, the DNS operates under the assumption
	facing authoritative name servers will respond to "usual" DNS queries		that public facing authoritative name servers will respond to "usual"
	for any zone they are authoritative for without further		DNS queries for any zone they are authoritative for without further
	authentication or authorization of the client (resolver). Due to the		authentication or authorization of the client (resolver). Due to the
	lack of search capabilities, only a given qname will reveal the		lack of search capabilities, only a given qname will reveal the
	resource records associated with that name (or that name's non		resource records associated with that name (or that name's non-
	existence). In other words: one needs to know what to ask for, in		existence). In other words: one needs to know what to ask for, in
	order to receive a response. The zone transfer qtype [RFC5936] is		order to receive a response. The zone transfer qtype [RFC5936] is
	often blocked or restricted to authenticated/authorized access to		often blocked or restricted to authenticated/authorized access to
	enforce this difference (and maybe for other, more dubious reasons).		enforce this difference (and maybe for other, more dubious reasons).
	Another differentiation to be considered is between the DNS data		Another differentiation to be considered is between the DNS data
	itself, and a particular transaction (i.e., a DNS name lookup). DNS		itself and a particular transaction (i.e., a DNS name lookup). DNS
	data and the results of a DNS query are public, within the boundaries		data and the results of a DNS query are public, within the boundaries
	described above, and may not have any confidentiality requirements.		described above, and may not have any confidentiality requirements.
	However, the same is not true of a single transaction or sequence of		However, the same is not true of a single transaction or sequence of
	transactions; that data is not/should not be public. A typical		transactions; that transaction is not/should not be public. A
	example from outside the DNS world is: the Web site of Alcoholics		typical example from outside the DNS world is: the Web site of
	Anonymous is public; the fact that you visit it should not be.		Alcoholics Anonymous is public; the fact that you visit it should not
			be.
	2.2. Data in the DNS request		2.2. Data in the DNS request
	The DNS request includes many fields but two of them seem		The DNS request includes many fields but two of them seem
	particularly relevant for the privacy issues, the qname and the		particularly relevant for the privacy issues, the qname and the
	source IP address. "source IP address" is used in a loose sense of		source IP address. "source IP address" is used in a loose sense of
	"source IP address + may be source port", because the port is also in		"source IP address + maybe source port", because the port is also in
	the request and can be used to sort out several users sharing an IP		the request and can be used to sort out several users sharing an IP
	address (CGN for instance).		address (behind a CGN for instance).
	The qname is the full name sent by the original user. It gives		The qname is the full name sent by the user. It gives information
	information about what the user does ("What are the MX records of		about what the user does ("What are the MX records of example.net?"
	example.net?" means he probably wants to send email to someone at		means he probably wants to send email to someone at example.net,
	example.net, which may be a domain used by only a few persons and		which may be a domain used by only a few persons and therefore very
	therefore very revealing). Some qnames are more sensitive than		revealing about communication relationships). Some qnames are more
	others. For instance, querying the A record of google-analytics.com		sensitive than others. For instance, querying the A record of
	reveals very little (everybody visits Web sites which use Google		google-analytics.com reveals very little (everybody visits Web sites
	Analytics) but querying the A record of www.verybad.example where		which use Google Analytics) but querying the A record of
	verybad.example is the domain of an illegal or very offensive		www.verybad.example where verybad.example is the domain of an illegal
	organization may create more problems for the user. Another example		or very offensive organization may create more problems for the user.
	is when the qname embeds the software one uses. For instance,		Also, sometimes, the qname embeds the software one uses, which could
	_ldap._tcp.Default-First-Site-Name._sites.gc._msdcs.example.org. Or		be a privacy issue. For instance, _ldap._tcp.Default-First-Site-
	some BitTorrent clients that query a SRV record for _bittorrent-		Name._sites.gc._msdcs.example.org. There are also some BitTorrent
			clients that query a SRV record for _bittorrent-
	tracker._tcp.domain.example.		tracker._tcp.domain.example.
	Another important thing about the privacy of the qname is the future		Another important thing about the privacy of the qname is the future
	usages. Today, the lack of privacy is an obstacle to putting		usages. Today, the lack of privacy is an obstacle to putting
	potentially sensitive or personally identifiable data in the DNS. At		potentially sensitive or personally identifiable data in the DNS. At
	the moment your DNS traffic might reveal that you are doing email but		the moment your DNS traffic might reveal that you are doing email but
	not who with. If your MUA starts looking up PGP keys in the DNS		not with whom. If your MUA starts looking up PGP keys in the DNS
	[I-D.wouters-dane-openpgp] then privacy becomes a lot more important.		[I-D.wouters-dane-openpgp] then privacy becomes a lot more important.
	And email is just an example; there will be other really interesting		And email is just an example; there would be other really interesting
	uses for a more privacy-friendly DNS.		uses for a more privacy-friendly DNS.
	For the communication between the stub resolver and the resolver, the		For the communication between the stub resolver and the recursive
	source IP address is the address of the user's machine. Therefore,		resolver, the source IP address is the address of the user's machine.
	all the issues and warnings about collection of IP addresses apply		Therefore, all the issues and warnings about collection of IP
	here. For the communication between the resolver and the		addresses apply here. For the communication between the recursive
	authoritative name servers, the source IP address has a different		resolver and the authoritative name servers, the source IP address
	meaning; it does not have the same status as the source address in a		has a different meaning; it does not have the same status as the
	HTTP connection. It is now the IP address of the resolver which, in		source address in a HTTP connection. It is now the IP address of the
	a way "hides" the real user. However, it does not always work.		recursive resolver which, in a way "hides" the real user. However,
	Sometimes [I-D.vandergaast-edns-client-subnet] is used (see its		hiding does not always work. Sometimes
	privacy analysis in [denis-edns-client-subnet]). Sometimes the end		[I-D.vandergaast-edns-client-subnet] is used (see its privacy
	user has a personal resolver on her machine. In that case, the IP		analysis in [denis-edns-client-subnet]). Sometimes the end user has
			a personal recursive resolver on her machine. In both cases, the IP
	address is as sensitive as it is for HTTP.		address is as sensitive as it is for HTTP.
	A note about IP addresses: there is currently no IETF document which		A note about IP addresses: there is currently no IETF document which
	describes in detail the privacy issues of IP addressing. In the mean		describes in detail the privacy issues of IP addressing. In the
	time, the discussion here is intended to include both IPv4 and IPv6		meantime, the discussion here is intended to include both IPv4 and
	source addresses. For a number of reasons their assignment and		IPv6 source addresses. For a number of reasons their assignment and
	utilization characteristics are different, which may have		utilization characteristics are different, which may have
	implications for details of information leakage associated with the		implications for details of information leakage associated with the
	collection of source addresses. (For example, a specific IPv6 source		collection of source addresses. (For example, a specific IPv6 source
	address seen on the public Internet is less likely than an IPv4		address seen on the public Internet is less likely than an IPv4
	address to originate behind a CGN or other NAT.) However, for both		address to originate behind a CGN or other NAT.) However, for both
	IPv4 and IPv6 addresses, it's important to note that source addresses		IPv4 and IPv6 addresses, it's important to note that source addresses
	are propagated with queries and comprise metadata about the host,		are propagated with queries and comprise metadata about the host,
	user, or application that originated them.		user, or application that originated them.
	2.3. Cache snooping		2.3. Cache snooping
	The content of resolvers can reveal data about the clients using it.		The content of recursive resolvers' caches can reveal data about the
			clients using it (the privacy risks depend on the number of clients).
	This information can sometimes be examined by sending DNS queries		This information can sometimes be examined by sending DNS queries
	with RD=0 to inspect cache content, particularly looking at the DNS		with RD=0 to inspect cache content, particularly looking at the DNS
	TTLs. Since this also is a reconnaissance technique for subsequent		TTLs. Since this also is a reconnaissance technique for subsequent
	cache poisoning attacks, some counter measures have already been		cache poisoning attacks, some counter measures have already been
	developed and deployed.		developed and deployed.
	2.4. On the wire		2.4. On the wire
	DNS traffic can be seen by an eavesdropper like any other traffic.		DNS traffic can be seen by an eavesdropper like any other traffic.
	It is typically not encrypted. (DNSSEC, specified in [RFC4033]		It is typically not encrypted. (DNSSEC, specified in [RFC4033]
	explicitely excludes confidentiality from its goals.) So, if an		explicitly excludes confidentiality from its goals.) So, if an
	initiator starts a HTTPS communication with a recipient, while the		initiator starts a HTTPS communication with a recipient, while the
	HTTP traffic will be encrypted, the DNS exchange prior to it will not		HTTP traffic will be encrypted, the DNS exchange prior to it will not
	be. When the other protocols will become more or more privacy-aware		be. When other protocols will become more and more privacy-aware and
	and secured against surveillance, the DNS risks to become "the		secured against surveillance, the DNS risks to become "the weakest
	weakest link" in privacy.		link" in privacy.
	What also makes the DNS traffic different is that it may take a		An important specificity of the DNS traffic is that it may take a
	different path than the communication between the initiator and the		different path than the communication between the initiator and the
	recipient. For instance, an eavesdropper may be unable to tap the		recipient. For instance, an eavesdropper may be unable to tap the
	wire between the initiator and the recipient but may have access to		wire between the initiator and the recipient but may have access to
	the wire going to the resolver, or to the authoritative name servers.		the wire going to the recursive resolver, or to the authoritative
			name servers.
	The best place, from an eavesdropper's point of view, is clearly		The best place to tap, from an eavesdropper's point of view, is
	between the stub resolvers and the resolvers, because he is not		clearly between the stub resolvers and the recursive resolvers,
	limited by DNS caching.		because traffic is not limited by DNS caching.
	The attack surface between the stub resolver and the rest of the		The attack surface between the stub resolver and the rest of the
	world can vary widely depending upon how the end user's computer is		world can vary widely depending upon how the end user's computer is
	configured. By order of increasing attack surface:		configured. By order of increasing attack surface:
	The resolver can be on the end user's computer. In (currently) a		The recursive resolver can be on the end user's computer. In
	small number of cases, individuals may choose to operate their own		(currently) a small number of cases, individuals may choose to
	DNS resolver on their local machine. In this case the attack surface		operate their own DNS resolver on their local machine. In this case
	for the stub resolver to caching resolver connection is limited to		the attack surface for the connection between the stub resolver and
	that single machine.		the caching resolver is limited to that single machine.
	The resolver can be in the IAP (Internet Access Provider) premises.
	For most residential users and potentially other networks the typical
	case is for the end user's computer to be configured (typically
	automatically through DHCP) with the addresses of the DNS resolver at
	the IAP. The attack surface for on-the-wire attacks is therefore
	from the end user system across the local network and across the IAP
	network to the IAP's resolvers.
	The resolver may also be at the local network edge. For many/most		The recursive resolver may be at the local network edge. For many/
	enterprise networks and for some residential users the caching		most enterprise networks and for some residential users the caching
	resolver may exist on a server at the edge of the local network. In		resolver may exist on a server at the edge of the local network. In
	this case the attack surface is the local network. Note that in		this case the attack surface is the local network. Note that in
	large enterprise networks the DNS resolver may not be located at the		large enterprise networks the DNS resolver may not be located at the
	edge of the local network but rather at the edge of the overall		edge of the local network but rather at the edge of the overall
	enterprise network. In this case the enterprise network could be		enterprise network. In this case the enterprise network could be
	thought of as similar to the IAP network referenced above.		thought of as similar to the IAP network referenced below.
	The resolver can be a public DNS service. Some end users may be		The recursive resolver can be in the IAP (Internet Access Provider)
	configured to use public DNS resolvers such as those operated by		premises. For most residential users and potentially other networks
	Google Public DNS or OpenDNS. The end user may have configured their		the typical case is for the end user's computer to be configured
	machine to use these DNS resolvers themselves - or their IAP may		(typically automatically through DHCP) with the addresses of the DNS
	choose to use the public DNS resolvers rather than operating their		recursive resolvers at the IAP. The attack surface for on-the-wire
	own resolvers. In this case the attack surface is the entire public		attacks is therefore from the end user system across the local
	Internet between the end user's connection and the public DNS		network and across the IAP network to the IAP's recursive resolvers.
	service.
			The recursive resolver can be a public DNS service. Some machines
			may be configured to use public DNS resolvers such as those operated
			by Google Public DNS or OpenDNS. The end user may have configured
			their machine to use these DNS recursive resolvers themselves - or
			their IAP may have chosen to use the public DNS resolvers rather than
			operating their own resolvers. In this case the attack surface is
			the entire public Internet between the end user's connection and the
			public DNS service.
	2.5. In the servers		2.5. In the servers
	Using the terminology of [RFC6973], the DNS servers (resolvers and		Using the terminology of [RFC6973], the DNS servers (recursive
	authoritative servers) are enablers: they facilitate communication		resolvers and authoritative servers) are enablers: they facilitate
	between an initiator and a recipient without being directly in the		communication between an initiator and a recipient without being
	communications path. As a result, they are often forgotten in risk		directly in the communications path. As a result, they are often
	analysis. But, to quote again [RFC6973], "Although [...] enablers		forgotten in risk analysis. But, to quote again [RFC6973], "Although
	may not generally be considered as attackers, they may all pose		[...] enablers may not generally be considered as attackers, they may
	privacy threats (depending on the context) because they are able to		all pose privacy threats (depending on the context) because they are
	observe, collect, process, and transfer privacy-relevant data." In		able to observe, collect, process, and transfer privacy-relevant
	[RFC6973] parlance, enablers become observers when they start		data." In [RFC6973] parlance, enablers become observers when they
	collecting data.		start collecting data.
	Many programs exist to collect and analyze DNS data at the servers.		Many programs exist to collect and analyze DNS data at the servers.
	From the "query log" of some programs like BIND, to tcpdump and more		From the "query log" of some programs like BIND, to tcpdump and more
	sophisticated programs like PacketQ [packetq] and DNSmezzo		sophisticated programs like PacketQ [packetq] and DNSmezzo
	[dnsmezzo]. The organization managing the DNS server can use this		[dnsmezzo]. The organization managing the DNS server can use these
	data itself or it can be part of a surveillance program like PRISM		data itself or it can be part of a surveillance program like PRISM
	[prism] and pass data to an outside attacker.		[prism] and pass data to an outside observer.
	Sometimes, these data are kept for a long time and/or distributed to		Sometimes, these data are kept for a long time and/or distributed to
	third parties, for research purposes [ditl], for security analysis,		third parties, for research purposes [ditl], for security analysis,
	or for surveillance tasks. Also, there are observation points in the		or for surveillance tasks. Also, there are observation points in the
	network which gather DNS data and then make it accessible to third-		network which gather DNS data and then make it accessible to third-
	parties for research or security purposes ("passive DNS		parties for research or security purposes ("passive DNS
	[passive-dns]").		[passive-dns]").
	2.5.1. In the resolvers		2.5.1. In the recursive resolvers
	Resolvers see all the traffic since there is typically no caching
	before them. They are, therefore, well situated to observe the		Recursive Resolvers see all the traffic since there is typically no
	traffic. To summarize: your resolver knows a lot about you. The		caching before them. To summarize: your recursive resolver knows a
	resolver of a large IAP, or a large public resolver can collect data		lot about you. The resolver of a large IAP, or a large public
	from many users. You may get an idea of the data collected by		resolver can collect data from many users. You may get an idea of
	reading the privacy policy of a big public resolver [1].		the data collected by reading the privacy policy of a big public
			resolver [1].
	2.5.2. In the authoritative name servers		2.5.2. In the authoritative name servers
	Unlike resolvers, authoritative name servers are limited by caching;		Unlike what happens for recursive resolvers, observation capabilities
	they see only a part of the requests. For aggregated statistics		of authoritative name servers are limited by caching; they see only
	("What is the percentage of LOC queries?"), this is sufficient; but		the requests for which the answer was not in the cache. For
	it may prevent an observer from seeing everything. Still, the		aggregated statistics ("What is the percentage of LOC queries?"),
	authoritative name servers see a part of the traffic, and this subset		this is sufficient; but it prevents an observer from seeing
	may be sufficient to violate some privacy expectations.		everything. Still, the authoritative name servers see a part of the
			traffic, and this subset may be sufficient to violate some privacy
			expectations.
	Also, the end user has typically some legal/contractual link with the		Also, the end user has typically some legal/contractual link with the
	resolver (he has chosen the IAP, or he has chosen to use a given		recursive resolver (he has chosen the IAP, or he has chosen to use a
	public resolver), while he is often not even aware of the role of the		given public resolver), while having no control and perhaps no
	authoritative name servers and their observation abilities.		awareness of the role of the authoritative name servers and their
			observation abilities.
	It is an interesting question whether the privacy issues are bigger		It is an interesting question whether the privacy issues are bigger
	in the root or in a large TLD. The root sees the traffic for all the		in the root or in a large TLD. The root sees the traffic for all the
	TLDs (and the huge amount of traffic for non-existing TLD), but a		TLDs (and the huge amount of traffic for non-existing TLDs), but a
	large TLD has less caching before it.		large TLDs has less caching before it.
	As noted before, using a local resolver or a resolver close to the		As noted before, using a local resolver or a resolver close to the
	machine decreases the attack surface for an on-the-wire eavesdropper.		machine decreases the attack surface for an on-the-wire eavesdropper.
	But it may decrease privacy against an observer located on an		But it may decrease privacy against an observer located on an
	authoritative name server. This authoritative name server will see		authoritative name server. This authoritative name server will see
	the IP address of the end client, instead of the address of a big		the IP address of the end client, instead of the address of a big
	resolver shared by many users. A possible solution is to have a		recursive resolver shared by many users.
	local resolver and to forward the cache misses to a big resolver.
	This "protection", when using a large resolver with many clients, is		This "protection", when using a large resolver with many clients, is
	no longer present if [I-D.vandergaast-edns-client-subnet] is used		no longer present if [I-D.vandergaast-edns-client-subnet] is used
	because, in this case, the authoritative name server sees the		because, in this case, the authoritative name server sees the
	original IP address (or prefix, depending on the setup).		original IP address (or prefix, depending on the setup).
	As of today, all the instances of one root name server, L-root,		As of today, all the instances of one root name server, L-root,
	receive together around 20,000 queries per second. While most of it		receive together around 20,000 queries per second. While most of it
	is junk (errors on the TLD name), it gives an idea of the amount of		is junk (errors on the TLD name), it gives an idea of the amount of
	big data which pours into name servers.		big data which pours into name servers.
	Many domains, including TLD, are partially hosted by third-party		Many domains, including TLDs, are partially hosted by third-party
	servers, sometimes in a different country. The contracts between the		servers, sometimes in a different country. The contracts between the
	domain manager and these servers may or may not take privacy into		domain manager and these servers may or may not take privacy into
	account. Whatever the contract, the third-party hoster may be honest		account. Whatever the contract, the third-party hoster may be honest
	or not but, in any case, it will have to follow its local laws. It		or not but, in any case, it will have to follow its local laws. It
	may be surprising for an end-user that requests to a given ccTLD may		may be surprising for an end-user that requests to a given ccTLD may
	go to servers managed by organisations outside of the country.		go to servers managed by organisations outside of the country.
			Also, it seems (TODO: actual numbers requested) that there is a
			strong concentration of authoritative name servers among "popular"
			domains (such as the Alexa Top N list). With the control (or the
			ability to sniff the traffic) of a few name servers, you can gather a
			lot of information.
	2.5.3. Rogue servers		2.5.3. Rogue servers
	A rogue DHCP server can direct you to a rogue resolver. Most of the		A rogue DHCP server, or a trusted DHCP server that has had its
	times, it seems to be done to divert traffic, by providing lies for		configuration altered by malicious parties, can direct you to a rogue
	some domain names. But it could be used just to capture the traffic		recursive resolver. Most of the times, it seems to be done to divert
	and gather information about you. Same thing for malwares like		traffic, by providing lies for some domain names. But it could be
	DNSchanger[dnschanger] which changes the resolver in the machine's		used just to capture the traffic and gather information about you.
	configuration.		Same thing for malware like DNSchanger[dnschanger] which changes the
			recursive resolver in the machine's configuration, or with
			transparent DNS proxies in the network that will divert the traffic
			intended for a legitimate DNS server (for instance
			[turkey-googledns]).
	3. Actual "attacks"		3. Actual "attacks"
	A very quick examination of DNS traffic may lead to the false		A very quick examination of DNS traffic may lead to the false
	conclusion that extracting the needle from the haystack is difficult.		conclusion that extracting the needle from the haystack is difficult.
	"Interesting" primary DNS requests are mixed with useless (for the		"Interesting" primary DNS requests are mixed with useless (for the
	eavesdropper) second and tertiary requests (see the terminology in		eavesdropper) second and tertiary requests (see the terminology in
	Section 1). But, in this time of "big data" processing, powerful		Section 1). But, in this time of "big data" processing, powerful
	techniques now exist to get from the raw data to what you're actually		techniques now exist to get from the raw data to what you're actually
	interested in.		interested in.
	Many research papers about malware detection use DNS traffic to		Many research papers about malware detection use DNS traffic to
	detect "abnormal" behaviour that can be traced back to the activity		detect "abnormal" behaviour that can be traced back to the activity
	of malware on infected machines. Yes, this research was done for the		of malware on infected machines. Yes, this research was done for the
	good but, technically, it is a privacy attack and it demonstrates the		good but, technically, it is a privacy attack and it demonstrates the
	power of the observation of DNS traffic. See [dns-footprint],		power of the observation of DNS traffic. See [dns-footprint],
	[dagon-malware] and [darkreading-dns].		[dagon-malware] and [darkreading-dns].
	Passive DNS systems [passive-dns] allow reconstruction of the data of		Passive DNS systems [passive-dns] allow reconstruction of the data of
	sometimes an entire zone. It is used for many reasons, some good,		sometimes an entire zone. It is used for many reasons, some good,
	some bad. It is an example of privacy issue even when no source IP		some bad. It is an example of a privacy issue even when no source IP
	address is kept.		address is kept.
	4. Legalities		4. Legalities
	To our knowledge, there are no specific privacy laws for DNS data.		To our knowledge, there are no specific privacy laws for DNS data.
	Interpreting general privacy laws like [data-protection-directive]		Interpreting general privacy laws like [data-protection-directive]
	(European Union) in the context of DNS traffic data is not an easy		(European Union) in the context of DNS traffic data is not an easy
	task and it seems there is no court precedent here.		task and it seems there is no court precedent here.
	5. Security considerations		5. Security considerations
	This document is entirely about security, more precisely privacy. A		This document is entirely about security, more precisely privacy. It
	document on requirments for DNS privacy is [I-D.hallambaker-dnse].		just lays down the problem, it does not try to set requirments (with
	Possible solutions to the issues described here are discussed in		the choices and compromises they imply), much less to define
	[I-D.ietf-dnsop-qname-minimisation] (qname minimization), in		solutions. A document on requirments for DNS privacy is
			[I-D.hallambaker-dnse]. Possible solutions to the issues described
	[I-D.bortzmeyer-dnsop-privacy-sol] (local caching resolvers,		here are discussed in other documents (currently too many to be
	gratuitous queries), [I-D.hzhwm-start-tls-for-dns] (encryption of		listed here).
	traffic), in [I-D.wijngaards-dnsop-confidentialdns] (encryption also)
	or in many other documents (there are many proposals to encrypt the
	DNS). Attempts have been made to encrypt the resource record data
	[I-D.timms-encrypt-naptr].
	6. Acknowledgments		6. Acknowledgments
	Thanks to Nathalie Boulvard and to the CENTR members for the original		Thanks to Nathalie Boulvard and to the CENTR members for the original
	work which leaded to this draft. Thanks to Ondrej Sury for the		work which leaded to this document. Thanks to Ondrej Sury for the
	interesting discussions. Thanks to Mohsen Souissi for proofreading		interesting discussions. Thanks to Mohsen Souissi and John Heidemann
	and to Warren Kumari for proofreading and many readability		for proofreading, to Paul Hoffman, Marcos Sanz and Warren Kumari for
	improvements. Thanks to Dan York, Suzanne Woolf, Tony Finch, Peter		proofreading, technical remarks, and many readability improvements.
	Koch and Frank Denis for good written contributions.		Thanks to Dan York, Suzanne Woolf, Tony Finch, Peter Koch and Frank
			Denis for good written contributions.
	7. References		7. References
	7.1. Normative References		7.1. Normative References
	[RFC1034] Mockapetris, P., "Domain names - concepts and facilities",		[RFC1034] Mockapetris, P., "Domain names - concepts and facilities",
	STD 13, RFC 1034, November 1987.		STD 13, RFC 1034, November 1987.
	[RFC1035] Mockapetris, P., "Domain names - implementation and		[RFC1035] Mockapetris, P., "Domain names - implementation and
	specification", STD 13, RFC 1035, November 1987.		specification", STD 13, RFC 1035, November 1987.
	[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate		[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
	Requirement Levels", BCP 14, RFC 2119, March 1997.		Requirement Levels", BCP 14, RFC 2119, March 1997.
	[RFC6973] Cooper, A., Tschofenig, H., Aboba, B., Peterson, J.,		[RFC6973] Cooper, A., Tschofenig, H., Aboba, B., Peterson, J.,
	Morris, J., Hansen, M., and R. Smith, "Privacy		Morris, J., Hansen, M., and R. Smith, "Privacy
	Considerations for Internet Protocols", RFC 6973, July		Considerations for Internet Protocols", RFC 6973, July
	2013.		2013.
	7.2. Informative References		[RFC7258] Farrell, S. and H. Tschofenig, "Pervasive Monitoring Is an
			Attack", BCP 188, RFC 7258, May 2014.
	[RFC2181] Elz, R. and R. Bush, "Clarifications to the DNS		7.2. Informative References
	Specification", RFC 2181, July 1997.
	[RFC4033] Arends, R., Austein, R., Larson, M., Massey, D., and S.		[RFC4033] Arends, R., Austein, R., Larson, M., Massey, D., and S.
	Rose, "DNS Security Introduction and Requirements", RFC		Rose, "DNS Security Introduction and Requirements", RFC
	4033, March 2005.		4033, March 2005.
	[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security
	(TLS) Protocol Version 1.2", RFC 5246, August 2008.
	[RFC5936] Lewis, E. and A. Hoenes, "DNS Zone Transfer Protocol		[RFC5936] Lewis, E. and A. Hoenes, "DNS Zone Transfer Protocol
	(AXFR)", RFC 5936, June 2010.		(AXFR)", RFC 5936, June 2010.
	[I-D.vandergaast-edns-client-subnet]		[I-D.vandergaast-edns-client-subnet]
	Contavalli, C., Gaast, W., Leach, S., and E. Lewis,		Contavalli, C., Gaast, W., Leach, S., and E. Lewis,
	"Client Subnet in DNS Requests", draft-vandergaast-edns-		"Client Subnet in DNS Requests", draft-vandergaast-edns-
	client-subnet-02 (work in progress), July 2013.		client-subnet-02 (work in progress), July 2013.
	[I-D.bortzmeyer-dnsop-privacy-sol]
	Bortzmeyer, S., "Possible solutions to DNS privacy
	issues", draft-bortzmeyer-dnsop-privacy-sol-00 (work in
	progress), December 2013.
	[I-D.ietf-dnsop-qname-minimisation]
	Bortzmeyer, S., "DNS query name minimisation to improve
	privacy", draft-ietf-dnsop-qname-minimisation-00 (work in
	progress), October 2014.
	[I-D.wijngaards-dnsop-confidentialdns]
	Wijngaards, W. and G. Wiley, "Confidential DNS", draft-
	wijngaards-dnsop-confidentialdns-01 (work in progress),
	March 2014.
	[I-D.timms-encrypt-naptr]
	Timms, B., Reid, J., and J. Schlyter, "IANA Registration
	for Encrypted ENUM", draft-timms-encrypt-naptr-01 (work in
	progress), July 2008.
	[I-D.hzhwm-start-tls-for-dns]
	Zi, Z., Zhu, L., Heidemann, J., Mankin, A., and D.
	Wessels, "Starting TLS over DNS", draft-hzhwm-start-tls-
	for-dns-00 (work in progress), February 2014.
	[I-D.hallambaker-dnse]		[I-D.hallambaker-dnse]
	Hallam-Baker, P., "DNS Privacy and Censorship: Use Cases		Hallam-Baker, P., "DNS Privacy and Censorship: Use Cases
	and Requirements.", draft-hallambaker-dnse-01 (work in		and Requirements.", draft-hallambaker-dnse-01 (work in
	progress), May 2014.		progress), May 2014.
	[I-D.wouters-dane-openpgp]		[I-D.wouters-dane-openpgp]
	Wouters, P., "Using DANE to Associate OpenPGP public keys		Wouters, P., "Using DANE to Associate OpenPGP public keys
	with email addresses", draft-wouters-dane-openpgp-02 (work		with email addresses", draft-wouters-dane-openpgp-02 (work
	in progress), February 2014.		in progress), February 2014.
	[dprive] IETF, ., "The DPRIVE working group", March 2014,		[I-D.hoffman-dns-terminology]
	<http://www.ietf.org/mail-archive/web/dns-privacy/>.		Hoffman, P., Sullivan, A., and K. Fujiwara, "DNS
			Terminology", draft-hoffman-dns-terminology-00 (work in
			progress), November 2014.
	[dnsop] IETF, ., "The DNSOP working group", October 2013,		[dprive] IETF, DPRIVE., "The DPRIVE working group", March 2014,
	<http://www.ietf.org/mail-archive/web/dnsop/>.		<http://www.ietf.org/mail-archive/web/dns-privacy/>.
	[denis-edns-client-subnet]		[denis-edns-client-subnet]
	Denis, F., "Security and privacy issues of edns-client-		Denis, F., "Security and privacy issues of edns-client-
	subnet", August 2013, <https://00f.net/2013/08/07/edns-		subnet", August 2013, <https://00f.net/2013/08/07/edns-
	client-subnet/>.		client-subnet/>.
	[dagon-malware]		[dagon-malware]
	Dagon, D., "Corrupted DNS Resolution Paths: The Rise of a		Dagon, D., "Corrupted DNS Resolution Paths: The Rise of a
	Malicious Resolution Authority", 2007, <https://www.dns-		Malicious Resolution Authority", 2007, <https://www.dns-
	oarc.net/files/workshop-2007/Dagon-Resolution-		oarc.net/files/workshop-2007/Dagon-Resolution-
	corruption.pdf>.		corruption.pdf>.
	[dns-footprint]		[dns-footprint]
	Stoner, E., "DNS footprint of malware", October 2010,		Stoner, E., "DNS footprint of malware", October 2010,
	<https://www.dns-oarc.net/files/workshop-201010/OARC-		<https://www.dns-oarc.net/files/workshop-201010/OARC-ers-
	ers-20101012.pdf>.		20101012.pdf>.
	[darkreading-dns]		[darkreading-dns]
	Lemos, R., "Got Malware? Three Signs Revealed In DNS		Lemos, R., "Got Malware? Three Signs Revealed In DNS
	Traffic", May 2013, <http://www.darkreading.com/monitoring		Traffic", May 2013,
	/got-malware-three-signs-revealed-in-dns/240154181>.		<http://www.darkreading.com/monitoring/
			got-malware-three-signs-revealed-in-dns/240154181>.
	[dnschanger]		[dnschanger]
	Wikipedia, ., "DNSchanger", November 2011,		Wikipedia, , "DNSchanger", November 2011,
	<http://en.wikipedia.org/wiki/DNSChanger>.		<http://en.wikipedia.org/wiki/DNSChanger>.
	[dnscrypt]		[packetq] Dot SE, , "PacketQ, a simple tool to make SQL-queries
	Denis, F., "DNSCrypt", , <http://dnscrypt.org/>.		against PCAP-files", 2011,
			<https://github.com/dotse/packetq/wiki>.
	[dnscurve]
	Bernstein, D., "DNScurve", , <http://dnscurve.org/>.
	[packetq] Dot SE, ., "PacketQ, a simple tool to make SQL-queries
	against PCAP-files", 2011, <https://github.com/dotse/
	packetq/wiki>.
	[dnsmezzo]		[dnsmezzo]
	Bortzmeyer, S., "DNSmezzo", 2009,		Bortzmeyer, S., "DNSmezzo", 2009,
	<http://www.dnsmezzo.net/>.		<http://www.dnsmezzo.net/>.
	[prism] NSA, ., "PRISM", 2007, <http://en.wikipedia.org/wiki/		[prism] NSA, , "PRISM", 2007, <http://en.wikipedia.org/wiki/
	PRISM_%28surveillance_program%29>.		PRISM_%28surveillance_program%29>.
	[crime] Rizzo, J. and T. Dong, "The CRIME attack against TLS",		[ditl] CAIDA, , "A Day in the Life of the Internet (DITL)", 2002,
	2012,		<http://www.caida.org/projects/ditl/>.
	<http://en.wikipedia.org/wiki/CRIME_(security_exploit)>.
	[ditl] CAIDA, ., "A Day in the Life of the Internet (DITL)",		[turkey-googledns]
	2002, <http://www.caida.org/projects/ditl/>.		Bortzmeyer, S., "Hijacking of public DNS servers in
			Turkey, through routing", 2014,
			<http://www.bortzmeyer.org/
			dns-routing-hijack-turkey.html>.
	[data-protection-directive]		[data-protection-directive]
	Europe, ., "European directive 95/46/EC on the protection		Europe, , "European directive 95/46/EC on the protection
	of individuals with regard to the processing of personal		of individuals with regard to the processing of personal
	data and on the free movement of such data", November		data and on the free movement of such data", November
	1995, <http://eur-lex.europa.eu/LexUriServ/		1995, <http://eur-lex.europa.eu/LexUriServ/
	LexUriServ.do?uri=CELEX:31995L0046:EN:HTML>.		LexUriServ.do?uri=CELEX:31995L0046:EN:HTML>.
	[passive-dns]		[passive-dns]
	Weimer, F., "Passive DNS Replication", April 2005,		Weimer, F., "Passive DNS Replication", April 2005,
	<http://www.enyo.de/fw/software/dnslogger/#2>.		<http://www.enyo.de/fw/software/dnslogger/#2>.
	[tor-leak]		[tor-leak]
	Tor, ., "DNS leaks in Tor", 2013, <https://		Tor, , "DNS leaks in Tor", 2013,
	trac.torproject.org/projects/tor/wiki/doc/TorFAQ#Ikeepseei		<https://trac.torproject.org/projects/tor/wiki/doc/TorFAQ#
	ngthesewarningsaboutSOCKSandDNSandinformationleaks.ShouldI		IkeepseeingthesewarningsaboutSOCKSandDNSandinformationleak
	worry>.		s.ShouldIworry>.
			[yanbin-tsudik]
			Yanbin, L. and G. Tsudik, "Towards Plugging Privacy Leaks
			in the Domain Name System", 2009,
			<http://arxiv.org/abs/0910.2472>.
			[castillo-garcia]
			Castillo-Perez, S. and J. Garcia-Alfaro, "Anonymous
			Resolution of DNS Queries", 2008,
			<http://deic.uab.es/~joaquin/papers/is08.pdf>.
			[fangming-hori-sakurai]
			Fangming, , Hori, Y., and K. Sakurai, "Analysis of Privacy
			Disclosure in DNS Query", 2007,
			<http://dl.acm.org/citation.cfm?id=1262690.1262986>.
			[federrath-fuchs-herrmann-piosecny]
			Federrath, H., Fuchs, K., Herrmann, D., and C. Piosecny,
			"Privacy-Preserving DNS: Analysis of Broadcast, Range
			Queries and Mix-Based Protection Methods", 2011,
			<https://svs.informatik.uni-hamburg.de/publications/2011/2
			011-09-14_FFHP_PrivacyPreservingDNS_ESORICS2011.pdf>.
			7.3. URIs
			[1] https://developers.google.com/speed/public-dns/privacy
	Author's Address		Author's Address
	Stephane Bortzmeyer		Stephane Bortzmeyer
	AFNIC		AFNIC
	1, rue Stephenson		1, rue Stephenson
	Montigny-le-Bretonneux 78180		Montigny-le-Bretonneux 78180
	France		France
	Phone: +33 1 39 30 83 46		Phone: +33 1 39 30 83 46
End of changes. 69 change blocks.
	262 lines changed or deleted		296 lines changed or added
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